Sensory Motor Amnesia (SMA) occurs when muscles are so tight that they just won't relax. Even when you think you are relaxed, enjoying yourself or doing nothing those shoulders, and hips, or back just doesn't relax. When nothing you do will relax those muscles long term you probably have Sensory Motor Amnesia.
The brain controls your muscles, and that connection between the brain and muscles can get stuck due to the brain's response to stress or trauma and it's constant reminder to muscles to tighten. Stress is an unavoidable part of life. Hanna discovered that it isn't the stress that causes muscular problems but the way we reflexively react to the stress over and over again throughout our lives.
Hanna observed that when muscles become habitually and involuntarily contracted due to real-life stress such as accidents, injuries, surgery, major illnesses and repetitive movements and even emotional situations, not only do those muscles lose their ability to relax, but the brain actually loses sensation of the muscles and forgets how to release them.
Muscles never move unless the brain gives them a signal to move. If your muscles keep getting the signal to contract they will remain in that position unless you intentionally relax them. Even if they don't remain in an actively contracted state you will probably develop an exaggerated level of muscular tension.
The end result of all of this is sore tight muscles, joint stiffness, a loss of smooth controlled movement and chronic pain.